Wave forcing combined to coastline retreat may weaken or unsettle coastal and port structures. Coupling between dynamic flow and seabed mechanical properties at the vicinity of a coastal structure may trigger scour and liquefaction phenomena leading to easier erosion. Field experiments in a macrotidal environment have shown that air bubbles can be trapped within the sand bed, as the beach desaturates at low tide and partially saturates during rising tide. The seabed gas content is of major influence on pore pressure transmission and hence on liquefaction occurrence. Detailed measurements and visualization of the seabed are not easily obtained in the field. A physical model is devised in order to reproduce the main physics of the seabed response to wave impact on a coastal structure.